To provide a method for keeping green cases while preventing the cases from being deformed, and a device therefore.

After transferring green cases 12 after molding to the green case keeping device 1, a plurality of divided segments 17 with a packing sheet 7 fitted to the outer periphery of a keeping drum 4 are diametrally expanded, so that the green case 12 is positioned by stoppers 5, 6 provided on the keeping drum 4. At the same time, the diametral expansion of the divided segments 17 results in the pressing of the beads parts 12a, 12b of the green case 12 in the outside-of-the diameter direction and the subsequent closed condition of a bore 9 ensues. Further, compressed air is introduced into the bore 9 from the air aperture 8 of the keeping drum 4 to make the inner pressure of the bore 9 higher than the outer pressure of the green case 12 and the green cases 12 are kept in such a condition.